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Related Concept Videos

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z Scores and Area Under the Curve

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Related Experiment Video

Updated: Jun 24, 2026

External Cephalic Version: Is it an Effective and Safe Procedure?
08:49

External Cephalic Version: Is it an Effective and Safe Procedure?

Published on: June 6, 2020

Estimating conception statistics using gestational age information from NHS Numbers for Babies data.

Yuan Huang Chow1, Nirupa Dattani

  • 1Office for National Statistics.

Health Statistics Quarterly
|March 27, 2009
PubMed
Summary
This summary is machine-generated.

New analysis using National Health Service (NHS) Numbers for Babies data reveals most maternities have conception timings differing from the assumed 38 weeks. Revised conception statistics for England and Wales show minimal impact on age-specific rates.

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Last Updated: Jun 24, 2026

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Area of Science:

  • Reproductive Health
  • Demography
  • Public Health Statistics

Background:

  • Current conception statistics for England and Wales assume all live births are 38 weeks gestation.
  • Gestation period information is not collected at birth registration, leading to this assumption.
  • This assumption may affect the accuracy of historical conception data.

Purpose of the Study:

  • To re-estimate conception statistics for England and Wales for the year 2005.
  • To incorporate actual gestational age data for improved accuracy.
  • To assess the impact of revised gestational age on age-specific conception rates.

Main Methods:

  • Utilized gestational age information from the National Health Service (NHS) Numbers for Babies (NN4B) dataset for the first time.
  • Re-estimated conception statistics based on this new data source.
  • Compared revised age-specific conception rates with those derived from the current methodology.

Main Results:

  • 72% of conceptions leading to a maternity had a gestational period different from the assumed 38 weeks.
  • The majority of these differing gestations were either 37 or 39 weeks.
  • Revised age-specific conception rates were not significantly different from current estimates.

Conclusions:

  • The assumption of 38 weeks gestation for all maternities is inaccurate for a significant majority of cases.
  • Incorporating actual gestational age data provides a more precise understanding of conception timings.
  • Despite variations in individual gestational periods, overall age-specific conception rates remain largely consistent.